Ventilated cigarettes are well known in which a multiplicity of perforations are provided either in the tipping paper surrounding the filter or some portion of the cigarette itself. Typical examples of such cigarettes are disclosed in U.S. Pat. Nos. 2,988,088; 2,980,116; and 3,410,274. The perforations provide a means for diluting the smoke drawn through the cigarette with ambient air resulting in a cooler, less harsh-tasting cigarette. It is also recognized that air dilution reduces the delivery of total particulate matter and gas phase constituents in the smoke.
Air dilution or attenuation of the mainstream smoke of the cigarette through the filter tip has become the most popular and widely accepted method of reducing smoke yield constituents of cigarettes. With filter tip cigarettes having perforated tipping, the practice is to pattern the perforations in a circumferential line or lines about the tipping so that the holes are positioned either directly over the filter or at the junction between the filter and the tobacco column. When the perforations are disposed over the filter, the filter plug itself is wrapped in a porous, air permeable plug wrap thereby allowing air to enter the filter via the tipping perforations and porous plug wrap where it mixes with the smoke. In such cases, the tipping paper and plug wrap are adhered together over areas of their contiguous surfaces except in the perforated region, which is left adhesive-free to prevent blocking of both the tipping perforations and the porous plug wrap. The conventional means of accomplishing the air dilution effect with a perforated tipping envelope is through the use of macroperforated tipping having clearly visible, relatively large holes. Usually the holes are punched in the paper by mechanically perforating the tipping paper prior to constructing the cigarette, although electrostatically perforated tipping papers having randomly spaced holes of irregular size are disclosed in West German Offenlegungsschrift No. 25 31 285. Such mechanically perforated tipping papers exhibit a band of one or more lines in discrete perforations which are clearly visible to the unaided eye.
It is also known to utilize a uniformly porous tipping envelope overlying a porous filter plug wrap to achieve air ventilation of the mainstream smoke from cigarettes, as disclosed in U.S. Pat. No. 3,805,800. With such construction, the porous tipping envelope and plug wrap are glued together over areas of their contiguous surfaces with at least one ventilated region left unglued so as to provide a porous area for air to enter the mainstream smoke in the cigarette, thus providing the desired ventilation.
While the heretofore known ventilated cigarettes reduce the delivery of total particulate matter and gas phase constituents in the cigarette smoke, they do not provide the degree of selective reduction desired with regard to some of the more undesirable constituents in cigarette smoke, such as carbon monoxide. Moreover, they tend to reduce nicotine yields to a similar extent as other constituents such that at maximum total reductions achievable, the nicotine level in the smoke is drastically reduced. With increased public concern over the amount of carbon monoxide present in cigarette smoke, this constituent has become of increasing importance to the industry. This invention offers an alternate means to either macroperforated or ultraporous tipping for achieving air dilution at the filter while at the same time achieving heretofore unobtainable selective reductions of carbon monoxide without excessive reduction of nicotine in the cigarette smoke.